Pregnancy Due Date Calculator
Calculate your estimated due date using Naegele's rule. Enter the first day of your last menstrual period (LMP) to find out when your baby is due, your current week of pregnancy, and which trimester you are in.
Trimester Breakdown
Pregnancy is divided into three trimesters, each lasting approximately 13 weeks:
| Trimester | Weeks | Key Developments |
|---|---|---|
| 1st Trimester | Weeks 1 – 12 | Embryo develops major organs, neural tube forms, heartbeat begins |
| 2nd Trimester | Weeks 13 – 26 | Baby grows rapidly, movements felt, gender can be determined |
| 3rd Trimester | Weeks 27 – 40 | Baby gains weight, lungs mature, preparation for delivery |
How the Due Date is Calculated
This calculator uses Naegele's rule, the standard method used by doctors worldwide to estimate the due date:
For example, if your last menstrual period started on January 1, 2026:
Important Notes
- -This calculation assumes a regular 28-day menstrual cycle
- -First trimester ultrasound is more accurate for dating pregnancy
- -Only about 5% of babies are born on the exact due date
- -A normal full-term delivery can happen between weeks 37 and 42
- -Always consult your obstetrician for the most accurate estimate
Frequently Asked Questions
How is the pregnancy due date calculated?
The most common method is Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day menstrual cycle with ovulation occurring on day 14. Your doctor may adjust the date based on ultrasound measurements.
How accurate is the estimated due date?
Only about 5% of babies are born on their exact due date. Most babies are born within 1-2 weeks before or after the estimated date. An ultrasound done in the first trimester can provide a more accurate estimate, often within 5-7 days of the actual delivery date.
What if my menstrual cycle is not 28 days?
If your cycle is longer or shorter than 28 days, the due date may shift accordingly. For example, if your cycle is 35 days, ovulation likely occurs around day 21 instead of day 14, which would push the due date forward by about a week. Inform your doctor about your cycle length for a more accurate estimate.
What are the trimesters of pregnancy?
Pregnancy is divided into three trimesters. The first trimester (weeks 1-12) involves major organ development. The second trimester (weeks 13-26) is when the baby grows rapidly and movements are felt. The third trimester (weeks 27-40) is when the baby gains weight and prepares for birth.
When should I see a doctor after finding out I am pregnant?
You should schedule your first prenatal visit as soon as you find out you are pregnant, ideally between weeks 6-8. Early prenatal care is important for monitoring the health of both mother and baby. You can book an appointment with an obstetrician on Zospital for expert guidance.
Related Health Resources
Medical Disclaimer
The content provided on Zospital is for general informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. If you think you may have a medical emergency, call your doctor or emergency services immediately.